1. Field of the Invention
This invention relates to a stereoscopic image signal processing device for processing stereoscopic image signals.
2. Description of the Related Art
FIG. 1 illustrates the main parts of a stereoscopic television apparatus which has been considered in the past. In the figure, 1R and 1L are respectively television cameras for shooting a scene at one time to produce video signals. The right-camera-eye image information signal is obtained from the television camera 1R, and the left-camera-eye one from the other camera 1L. An output selector circuit 2 is receptive of the above-described right- and left-camera-eye image information signals from the television cameras 1R and 1L and puts them on its output line alternately in synchronized relation to a synchronizing signal of 60 Hz from a synchronizing signal generator circuit 3. The stereoscopic image signal produced from the output selector circuit 2 is amplified by an amplifier 4. A television set 5 of, for example, NTSC system receives the output of the amplifier 4 and reproduces images for a stereoscopic picture. In this case, the right-camera-eye image appears in the odd-numbered field of a picture frame on the television set 5, and the left-camera-eye image appear in the even-numbered field of the picture frame. A synchronizing signal separation circuit 6 separates out the vertical synchronizing signal (60 Hz) from the stereoscopic image signal produced from the amplifier 4 to produce a pulse signal of 60 Hz. Light-shutters 7R and 7L are mounted on the right and left sides of the rim of a pair of viewing spectacles 8 for the stereoscopic picture. A shutter drive circuit 9 operates in such a manner that the right light shutter 7R is opened, while the left light shutter 7L is closed, in synchronism with the synchronizing signal produced from the synchronizing signal separation circuit 6 when the left-camera-eye image of the picture frame is reproduced on the display surface of the television set 5, and the light shutters 7R and 7L are closed and opened respectively, when the right-camera-eye image is reproduced.
In operating the prior known stereoscopic television apparatus of such a constructional feature, when a scene, for example, as shown in FIG. 2, a car C moving across the front of a tree T (background) from right to left, is shot by the television cameras 1R and 1L at one time, their video signals alternately go out from the output selector circuit 2 in synchronism with the output of the synchronizing signal generator circuit 3, and the sequence of the right- and left-camera-eye image signals alternating with each other is applied through the amplifier 4 to the television set 5. Thus, the right-and left-camera-eye images are presented in, for example, the even- and odd-numbered fields of a frame on the television set 5 respectively. An example of the reproduced stereoscopic picture is shown in FIG. 3.
When the right- and left-camera-eye images on the display surface of the television set 5 are viewed through the pair of spectacles 8 whose light-shutters 7R and 7L are alternately driven to open and close by the shutter drive circuit 9 (see FIG. 4), light radiating from the right-camera-eye image, for example, indicated at 4a in FIG. 3, passes through the opened light-shutter 7L to the left eye El of an observer P, while light radiating from the left-camera-eye image 4b passes through the opened light shutter 7R to the right eye Er of the observer P. Hence, that image of the car C in the left eye El which lies on the right side of the image of the tree T and that image of the same car C in the right eye Er which lies on the left side of the image of the tree T are superimposed by the afterimage effect so that, as shown in FIG. 5, the observer P perceives the scene stereoscopically as if the image of the car C were nearer to him than the tree T. The larger the visual difference of the right and left eyes, the longer the distance between the car and tree in the stereoscopic picture can be perceived.
The conventional stereoscopic television apparatus could work well only when the viewer wore the light-shutter spectacles. If he took off his stereoscopic spectacles and viewed directly its television set to get the surface image as in the ordinary television set, a problem arose that, because its feature is to alternately reproduce the right and left images in the same display surface of the television set, they were seen as superimposed one upon another. Thus, what was not stereoscopic, or as in the ordinary television set, could not be seen.